Lightning-arrester



A. W. COPLEY. LIGHTNING ARRESTER. APPLICATION man SEPT. I. 1917.

1,361,967, Patented Dec. 14, 1920.

WITNESSES:

INVENTOR WM. A/mw W Cop/a;

ALMON w. GOPLEY, or HOUSE ELECTRIC & SYLVANIA.

WILKINSBURG, PENNSYLVANIA, ASSIGNOR TO WESTING- MANUFACTURING COMPANY, A CORPORATION OF PENN- LIGHTNING-ARRESTER.

Specification of Iietters Patent.

Patented Dec. 14, 1920.

Application filed September 1, 1917. Serial No. 189,355.

To all whom it may concern Be it known that I, ALMoN V. CorLnY, a citizen of the United States, and a resident of \Vilkinsburg, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Lightning-Arresters, of which the following is a specification.

My invention relates to lightning arresters of the discharge-gap type, and it has for its object to provide-apparatus acter designated which shall be .strong and durable in construction, simple and inexpensive to manufacture, and in which an exceedingly small discharge gap may be formed.

An important Characteristic of my invention is that it is adapted for use in arresters having several discharge gaps connected to different portions of a circuit and so constructed and related that the breaking down of one of the gaps causes or tends to cause the other gaps to break down also.

Heretofore, considerable trouble has been experienced in using lightning arresters of the low-voltage type, that is of the vacuum and air-gap types; The objection to a vacuum-type arrester is, that the vacuum may be impaired while in service, thereby eliminating the protection afforded by the arrester, without warning. The objection to the usual form of an air-gap type arrester is that it is difiicult to make the air gap small enough for a low-voltage breakdown and, at the same time, make the apparatus of simple construction. Arresters of the usual types are also objectionable for use on telephone circuits because a breakdown of the gap connected to one of the lines freuently causes current to flow from the other line through the telephone apparatus to reach the ground.

It has been customary, especially in lightning arresters adapted for use in telephone circuits, to space two blocks of carbon apart by means of perforated insulating members composed of mica, thus forming a discharge gap the length of which is equal to the thickness of the mica. My invention consists, broadly, in substituting for the above mentioned spacing member an insulating oxid film formed on one of the dischargegap members, which may be made of a thinness unattainable with a separate insulating member.

of the char-' The single figure of the accompanying drawing is a diagrammatic view of an elect'rlcal'system embodying one form of my invention. The arrester comprises two electrodes 1 and 2, which are connected to opposite sides of a circuit 3 here shown as a telephone circuit. A thin aluminum electrode 4, having portions of its surfaces provided with coatings 5 of insulating material, separates the electrodes 1 and 2 from each other. The upper end of the electrode et has no coating, and, therefore, paths are provided for the flow of current through the electrodes 1, 2 and l to ground, shown at (3.

The arrester is constructed by forming i11- sulating coatings 5 upon two sides of the electrode l and so combining the coated elec trode with the electrodes 1 and 2 that the latter shall be held in contact with the upper ends of the coatings, so that, where the said coatings are omitted at the top of the electrode, the lengths of the air gaps will be substantially equal to the thickness of the coatings. In this manner, a compact arrester having an exceedingly small air gap is provided. The discharge gaps may be made of any desired length by varying the thickness of the coatings 5. Since the two gaps are very close together, if excessive voltages be impressed upon both sides of the line and one of the discharge gaps breaks down, the other, on account of the ionization of the medium surrounding the gap, will break down at once.

The insulating oxid films 5 on the electrode t may be formed by immersing the electrode in a suitable electrolyte and passing current from the electrolyte to the electrode. Although any metal on which an oxid film can be formed may be employed in apparatus constructed in accordance with my invention, it has been found that aluminum is most suitable for this purpose on account of the ease with which such films may be formed thereon.

Although I have shown but one form of my invention and have described, in detail, one application of the same, it will be obvious to those skilled in the art that it is not so limited but is applicable to any combination of electrodes wherein the length of the air gap is determined by the thickness of an insulating film deposited on one of the electrodes, and I desire that only such limitations shall be placed thereupon as'are imposed by the prior art or are specifically set forth in the appended claims.

I claim as my invention:

1. A discharge gap for a lightning arrester comprising an electrode provided with an arcing surface partially covered with an insulating film, and an additional electrode provided with an oppositely disposed arcing surface spaced from said first named arcing surface by means of said film.

2. A discharge gap for a lightning arrester comprising a metallic electrode provided with an arcing surface partially cov- 4. A discharge gap for a lightning arrester comprising an aluminum electrode provided with an arcing surface partially covered with an insulating oxid film, and an additional electrode provided with an oppositely disposed arcing surface spaced from said first named arcing surface by means of said film.

5. A discharge gap for a lightning arrest-er comprising a plurality of electrodes,

one of which is composed of aluminum, is connected to ground, and is provided with an arcing surface partially covered with an insulating OXl(l film, and a plurality of additional electrodes adapted to be connected .to different current-carrying lilies, each of said additional electrodes being provided with arcing surfaces disposed oppositely to the arcing surface of said aluminum electrode and spaced therefrom by means of said insulating film.

In testimony whereof I have hereunto subscri ped my name this 21st day of August, 191

ALMON W. COPLEY. 

